Whether 4k is worth it depends a lot on the size of the TV vs how far away you sit. For a 65" TV, I don't see much difference between 4k/1080p above ~8ft away.
HDR is indeed effectively a marketing gimmick on many cheap TVs. They are getting better though
Also the content being viewed. High bandwidth 1080p can look sharper than over-compressed 4k.
It’s why even non-4k BluRays sometimes look better than streaming.